Marycarmen Godínez-Victoria

Stress modulates intestinal secretory immunoglobulin A

Stress is a response of the central nervous system to environmental stimuli perceived as a threat to homeostasis. The stress response triggers the generation of neurotransmitters and hormones from the hypothalamus pituitary adrenal axis, sympathetic axis and brain gut axis, and in this way modulates the intestinal immune system. The effects of psychological stress on intestinal immunity have been investigated mostly with the restraint/immobilization rodent model, resulting in an up or down modulation of SIgA levels depending on the intensity and time of exposure to stress. SIgA is a protein complex formed by dimeric (dIgA) or polymeric IgA (pIgA) and the secretory component (SC), a peptide derived from the polymeric immunoglobulin receptor (pIgR). The latter receptor is a transmembrane protein expressed on the basolateral side of gut epithelial cells, where it uptakes dIgA or pIgA released by plasma cells in the lamina propria. As a result, the IgA-pIgR complex is formed and transported by vesicles to the apical side of epithelial cells. pIgR is then cleaved to release SIgA into the luminal secretions of gut. Down modulation of SIgA associated with stress can have negative repercussions on intestinal function and integrity. This can take the form of increased adhesion of pathogenic agents to the intestinal epithelium and/or an altered balance of inflammation leading to greater intestinal permeability. Most studies on the molecular and biochemical mechanisms involved in the stress response have focused on systemic immunity. The present review analyzes the impact of stress (mostly by restraint/immobilization, but also with mention of other models) on the generation of SIgA, pIgR and other humoral and cellular components involved in the intestinal immune response. Insights into these mechanisms could lead to better therapies for protecting against pathogenic agents and avoiding epithelial tissue damage by modulating intestinal inflammation.

Effects on secretory IgA levels in small intestine of mice that underwent moderate exercise training followed by a bout of strenuous swimming exercise

Intestinal homeostasis effectors, secretory IgA (SIgA) and polymeric immunoglobulin receptor (pIgR), have been evaluated in proximal and distal small intestine with moderate-exercise training but not with strenuous exercise or a combination of these two protocols. Therefore, two groups of mice (n=6-8) were submitted to strenuous exercise, one with and one without previous training. The control group had no exercise protocol. Assessment was made of intestinal SIgA and plasma adrenal hormones (by immunoenzymatic assay), alpha-chain and pIgR proteins in intestinal mucosa (by Western blot), lamina propria IgA plasma-cells (by cytofluorometry), mRNA expression (by real-time PCR) for pIgR, alpha- and J-chains in liver and intestinal mucosa, and pro- and anti-inflammatory cytokines in mucosa samples. Compared to other exercise protocols, training plus strenuous exercise elicited: (1) higher levels of SIgA and pIgR in the proximal intestine (probably by hepatobiliary contribution); (2) higher levels of SIgA in the distal segment; (3) lower mRNA expression of some SIgA- and most pro-inflammatory pIgR-producing cytokines. SIgA and pIgR in both segments were derived from an existing pool of their corresponding producing cells. The apparent decreased translation of mRNA transcripts underlies lower levels of SIgA and pIgR in distal than proximal small intestine. There was no significant difference in the relatively high adrenal hormone levels found in both exercised groups. Further study is required about the effects of training plus strenuous exercise on pool-derived SIgA levels and mRNA expression of pro-inflammatory pIgR-producing cytokines. These results could have important implications for intestinal disorders involving inflammation and infection.

Repeated Restraint Stress Reduces the Number of IgA-Producing Cells in Peyer’s Patches

The few reports that have analyzed the effects of stress on the immune cells of the intestinal mucosa or the functions of these cells have tended to focus on S-IgA levels in saliva, and these studies have shown contradictory results. The principal objective of this study was to analyze the effects of repeated restraint stress on the number and distribution of immune cells in Peyer’s patches (PPs) as well as the effects of glucocorticoid and catecholamine administration on the same stress-related parameters. Upon analyzing the effect of repeated restraint stress on PPs, it was found that there was no modification in the morphological structure of the PPs but that restraint stress reduced the total number of lymphocytes and the number of CD8+ T cells, B cells, and plasma cells in PPs. Only at the site of PPs where IgA-producing plasma cells are most numerous (the dome) was a decrease found in this type of cell. These effects were due at least in part to the effect of glucocorticoids and catecholamines. Since IgA produced in PPs is a natural antibody that impedes bacterial infections, repeated stress may favor the entry of pathogens through the intestine.

Effects of restraint stress on NALT structure and nasal IgA levels.

The effects of stress on the mucosal immune responses in inflammatory disorders of the gut, as well as on salivary and intestinal IgA levels are well known. However, its effects on the structure and function of the NALT have not yet been reported, and are examined in the present study. Balb/c mice were submitted to restraint stress for 3h per day during 4 or 8d. The immunohistochemistry and flow cytometric analysis revealed that repeated restraint stress (4 and 8d) decreased the percentage, compared to the control group, of CD3(+) and CD4(+) T cells, without affecting the percentage of CD8(+) T cells or B220(+) cells (B cells). The numbers of IELs (CD4(+) and CD8(+) T cells) were lower at 4d of stress and higher at 8d. IgA(+) cells in NALT and nasal IgA levels showed a similar pattern, being significantly lower at 4d of stress and significantly higher at 8d. In summary, repeated restraint stress altered the distribution and number of lymphocytes and IgA(+) cells in nasal mucosa, probably due to changes in norepinephrine and corticosterone levels.

Intermittent fasting modulates IgA levels in the small intestine under intense stress: A mouse model

Intermittent fasting prolongs the lifespan and unlike intense stress provides health benefits. Given the role of the immunoglobulin A (IgA) in the intestinal homeostasis, the aim of this study was to assess the impact of intermittent fasting plus intense stress on secretory IgA (SIgA) production and other mucosal parameters in the duodenum and ileum. Two groups of six mice, with intermittent fasting or fed ad libitum for 12weeks, were submitted to a session of intense stress by a bout of forced swimming. Unstressed ad libitum fed or intermittently fasted groups were included as controls. After sacrifice, we evaluated intestinal SIgA and plasma adrenal hormones, lamina propria IgA+ plasma-cells, mRNA expression of polymeric immunoglobulin receptor, α- and J-chains in the liver and intestinal mucosa, as well as pro- (tumor necrosis factor-α, interleukin-6 and Interferon-γ) and anti- (interleukin-2, -4, -10 and transforming growth factor-β) inflammatory cytokines in mucosal samples. Under intense stress, intermittent fasting down- or up-modulated the levels of most parameters in the duodenum and ileum, respectively while up-regulated corticosterone levels without affecting epinephrine. Our data suggest intermittent fasting plus intense stress elicited neuroendocrine pathways that differentially controlled IgA and pIgR expression in duodenum and ileum. These findings provide experimental foundations for a presumable impact of intermittent fasting under intense stress on the intestinal homeostasis or inflammation by triggering or reducing the IgA production in ileum or duodenum respectively.

Nasal IgA secretion in a murine model of acute stress. The possible role of catecholamines.

Stress stimuli affect the immune system of the mucosa, and in particular IgA secretion. It is well documented that intense psychological and physical stress can increase susceptibility to infection by diverse pathogens in the upper respiratory tract. Our workgroup reported that chronic stress caused by immobilization elicits a decrease in nasal IgA levels in mice. Here, we explore how acute stress (caused by 4h of immobilization) affects IgA secretion in the nasal mucosa, and the possible role of the sympathetic nervous system in this effect. Nine-week-old male CD1 mice were divided into four groups: control, chemical sympathectomy (with 6-OHDA) and treatment with nadolol (5mg/kg) or phentolamine (15mg/kg). All these groups were subdivided into stressed and unstressed animals. The parameters evaluated included plasma corticosterone and epinephrine (only in control groups), SIgA levels (by ELISA) and SIgA expression (by Western Blot) in nasal fluid, percentage of IgA+ plasma cells, and mRNA expression of heavy alpha chain, pIgR, TNFα and TGFβ in nasal mucosa. Acute stress reduced the percentage of IgA+ cells while increasing the levels of IgA, the two hormones, and the mRNA expression of heavy alpha chain, pIgR, TNFα and TGFβ, which resulted in greater synthesis and transport of IgA. The treatments with 6-OHDA and α- and β-adrenergic receptor blockers suggest that sympathetic innervation by both types of adrenergic receptors is important for the control of SIgA secretion in nasal mucosa during acute stress. The increase in this parameter depended on the cytokines involved in IgA synthesis and transport.

Moderate exercise enhances expression of SIgA in mouse ileum.

The immune-suppression caused by acute stress can be reduced by a regular practice of moderate exercise which is known to modulate the expression of secretory-IgA. This antibody is essential for protection against infections and maintenance of homeostasis at the mucosal level. In order to explore the effects of moderate exercise on secretory-IgA production in ileum of the small intestine, 2 groups of mice were submitted to this protocol for 6 months, an exercise group and a sedentary group. After sacrifice, levels of secretory-IgA in intestinal fluid and levels of adrenal hormones in serum were determined by enzyme immunoenzymatic assay. IgA-plasma cells in lamina propria were evaluated by flow cytometry. Transcriptional mRNA expression in mucosa of alpha-chain, J-chain, pIgR and cytokines (Interleukin-2, -4, -6, -10, transforming growth factor-beta, interferon-gamma and tumor necrosis factor) were determined by RT-PCR. In comparison with sedentary mice, moderate exercised mice displayed an up-regulating effect on the production of secretory-IgA and IgA-plasma cells, on the expression of all mRNA transcripts from secretory-IgA associated proteins, and on all cytokines tested. However, serum levels of adrenal hormones were not altered. Future studies on secretory-IgA production are necessary to support the substantive effect of moderate exercise on protection and homeostasis at the intestinal level.

Effect of Bovine Lactoferrin Treatment Followed by Acute Stress on the IgA-Response in Small Intestine of BALB/c Mice

ABSTRACT Secretory IgA (SIgA) has a pivotal role in gut homeostasis, which can be disturbed by stress. SIgA is formed by IgA-dimers (associated by the J-chain) and the secretory component, a protein derivative of polymeric immunoglobulin receptor (pIgR). Given the gut immuno-modulatory properties of bovine lactoferrin (bLf), the aim of this study was to compare, after bLf treatment followed by acute stress, the IgA response and IgA-associated parameters in proximal versus distal small intestine. Male BALB/c mice (n = 6) were orally treated with bLf (50, 500, and 5000 μg) for 7 days, then stressed by immobilization for 1 h, and sacrificed. In proximal and distal segments, levels were determined of IgA in gut secretions (enzyme-linked immunosorbent assay [ELISA]), the α-/J-chain and pIgR proteins in epithelial cells (Western-blot), and mRNA expression of the α-/J-chain, pIgR, and interleukins (ILs) in mucosa (RT-PCR). Data were compared by two-way analysis of variance (ANOVA) (significance at P < 0.05). Under acute stress, bLf triggered higher levels of IgA, SIgA, and anti-bLf-IgA as well as greater mRNA expression of pIgR, IL-4, and IL-6 (500 µg) in proximal intestine, while inducing higher levels of the total IgA, α-/J-chain, and pIgR proteins as well as greater mRNA expression of the α-chain and IL-4 (5000 µg) in distal intestine. Compared to unstressed/bLf-untreated mice, plasma corticosterone (a stress biomarker, measured by ELISA) increased in stressed/bLf-treated (0, 50 and 500 µg) and unstressed/bLf-treated (5000 µg) mice. The interplay of corticosterone with gut neuroendocrine factors may have elicited signals creating anti-inflammatory conditions for an IgA-response profile in each intestinal region, according to the bLf concentration administered.

Intermittent fasting promotes bacterial clearance and intestinal IgA production in Salmonella typhimurium-infected mice.

The impact of intermittent fasting versus ad libitum feeding during Salmonella typhimurium infection was evaluated in terms of duodenum IgA levels, bacterial clearance and intestinal and extra‐intestinal infection susceptibility. Mice that were intermittently fasted for 12 weeks or fed ad libitum were infected with S. typhimurium and assessed at 7 and 14 days post‐infection. Next, we evaluated bacterial load in the faeces, Peyers patches, spleen and liver by plate counting, as well as total and specific intestinal IgA and plasmatic corticosterone levels (by immunoenzymatic assay) and lamina propria IgA levels in plasma cells (by cytofluorometry). Polymeric immunoglobulin receptor, α‐ and J‐chains, Pax‐5 factor, pro‐inflammatory cytokine (tumour necrosis factor‐α and interferon‐γ) and anti‐inflammatory cytokine (transforming growth factor‐β) mRNA levels were assessed in mucosal and liver samples (by real‐time PCR). Compared with the infected ad libitum mice, the intermittently fasted infected animals had (1) lower intestinal and systemic bacterial loads; (2) higher SIgA and IgA plasma cell levels; (3) higher mRNA expression of most intestinal parameters; and (4) increased or decreased corticosterone levels on day 7 and 14 post‐infection, respectively. No contribution of liver IgA was observed at the intestinal level. Apparently, the changes following metabolic stress induced by intermittent fasting during food deprivation days increased the resistance to S. typhimurium infection by triggering intestinal IgA production and presumably, pathogen elimination by phagocytic inflammatory cells.

Comparative pharmacokinetics and pharmacodynamics after subcutaneous and intramuscular administration of medroxyprogesterone acetate (25 mg) and estradiol cypionate (5 mg)

BACKGROUND The efficacy of contraceptives is affected by its route and ease of administration. Herein, both pharmacokinetics and pharmacodynamics of the once-a-month combined injectable contraceptive medroxyprogesterone acetate (MPA) plus estradiol cypionate (E(2)-Cyp) were compared after intramuscular (IM) or subcutaneous (SC) injection in women of reproductive age. STUDY DESIGN Thirty women were randomly assigned to the SC (n=15) or IM (n=15) route of MPA 25 mg+E(2)-Cyp 5 mg administration. Serum samples were obtained daily for 7 days and then three times a week for 40 days in order to quantify E(2), progesterone and MPA. In addition, three ultrasounds were performed on each subject to determine follicular development, and a daily record of the bleeding pattern and side effects was maintained. RESULTS A comparative analysis showed that the main pharmacokinetic (peak serum concentration, peak serum time, area under the serum concentration vs. time curve, absorption half-life and elimination half-life) and pharmacodynamic parameters, such as follicular development and ovulation, were similar in the SC vs. IM groups. Complete suppression in ovarian function was present in all women. The bleeding patterns and side effects were similar in both groups. CONCLUSIONS The results presented herein demonstrate that the injection of 25 mg of MPA plus 5 mg of E(2)-Cyp has similar efficacy and safety with either the SC or IM route of administration. The SC option can be considered a viable self-administered contraceptive option that might increase womens compliance to contraceptive use.